Magnetron tube structure



Dem. 1957 K. STEIMEL ,817,789

MAGNETRON TUBE STRUCTURE Filed Dec. 7, 1955 or the interaction space.

United States PatentO MAGNETRON TUBE STRUCTURE Karl Steimel, Ulm (Danube), Germany, assignor to Telefunken Gesellschaft fuer drahtlose Telegraphic G. in. b. H., Hannover, Germany Application December 7, 1953, Serial No. 396,557

Claims priority, application Germany December 8, 1952 9 fllaims. (Cl. 315-3953) The present invention relates to a high frequency signal generator, and in particular to a .high frequency signal generator of the magnetron tube type.

It has been well established that there exists a limitingvalue to the output power which may be obtained from a specific magnetron type tube structure. This value is determined both by the dimension and the thermal capacity of the electrodes of .the magnetron tube.

There are several known ways to increase the power output which may be obtained from a magnetron type tube. For instance, it is known that in order to obtain a greater output power one may increase the dimensions of the electrodes used in the magnetron tube. From experience it has been found however that a continuous increase ot the dimensions of the electrodes of the magnetron tube leads to a point wherea further increase in the size of the electrodes will not result in increased power output. In other words a saturation point will be reached.

Others skilled in the art have attempted to increase the power output which may be obtained from a magnetron tube by increasing in radial direction the discharge space, It has been found however that an increase of the discharge space in radial direction, where the number of cavity segments are maintained constant, leads to the requirement of a higher anode voltage supply which of course results in increased operating costs as well as increased danger to personnel.

If on the other hand the output power of the magnetron is to be increased without increasing the supply voltage,

sible to increase the number of anode segmentsbeyond twelve primarily because as the number of segments are increased, the number of oscillatory modes'which can be excited likewise increases while at the same time a smaller frequency gap will be found to exist between oscillatory modes. In other words, when the number of anode segments are increased a smaller frequency band separation will be found to exist within which no oscillations will be generated. A small frequency separation between two neighboring modes is highly undesirable since the electronic discharge maybe unable to decide which of the modes to operate in, and as a result there may be power emitted in two or more frequencies thus making operation of the magnetron tube very unsatisfactory.

Still others skilled in the art havehttempted to increase the output power from a magnetron tube by increasing the discharge space of the tube in axial direction. In theory, it would seem to b'epossihle to increase the discharge space in axial direction to any desired length since it has been consistently maintained that an infinitely long cylindrical discharge path can be used for magnetron tubes. However, experience has shown that practical limitations to the length of the discharge.

21,817,789 Patented Dec. 24, 1957 path do exist. For a discharge path which is large com pared to the operating wave length, oscillations may be excited in the magnetron tube by non-uniform fields along the axis of the electrode system. As a result, the operation of and the output from the magnetron tube is so detrimentally aifected that it has been found from experience that no advantage is obtained by making the discharge path longer than one fifth of the operating wave length of the magnetron tube.

It is an object of the present invention to provide a magnetron structure capable of generating high frequency oscillations at higher power levels than possible with currently used magnetron structures.

Still yet another object of the present invention is to provide a magnetron tube structure which operates in a stable and not an erratic manner.

Yet still another object of the present invention is to provide a magnetron structure including a multi-electrode system, each of which is magnetically and electrically isolated from adjoining electrode systems so that no in teraction can take place therebetween.

With the above objects in viewthe present invention mainly consists of a magnetron tube comprising a vacuum tight envelope, and a plurality of electrode systems each comprising a cathode portion having an electron emissive coating and an anode block divided into segments surrounding the electron emissive cathode portion, the segments of each block being uniformly spaced from each other angularly about the electron emissive cathode portion, all of the electron emissive cathode portions being arranged along a commonaxis, and each pair of adjoining blocks being located along the common axis adjacent to and angularly displaced with respect to each other by an angle equal to one-half the angular distance between adjoining segments of any one block.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connectionwith the accompanying drawings, in which:

Fig. l is a fragmentary developed sectional view taken along a line passing through the centers of the anode segments of a magnetron tube structure in accordance with the invention;

Fig. 2a is a vertical section takenthrough the axis of part of a magnetron tube in accordance with the present invention; and

Fig. 2b is a plan view of one-half of part of a magnetron tube structure in accordance with the present invention.

Referring to the drawing and first to Fig. 1, the anode segments of two electrode systems are shown in a fragmentary developed sectional view in the plane of the drawing. The segments of one of the electrode systems are designated by the reference numeral 1, and the segments of the other electrode system are designated by the reference numeral 2. Both electrode systems are arranged along the principal axis of the tube adjacent to and spaced from each other by a distance d, which may also be equal to zero. The segments 1 and 2 of the adjacent electrode systems are in turn arranged concentrically about a cathode, see Figs. 2a and 2b, having an axiscoinciding with the principal axisof the tube. If one considers the distance between the mid-point of. one anode segment to the mid-point of the adjacentanode segments as being equal to s, then it is apparent thatuthe anode segments 2 are displaced from the anode segments 1 by a distance or one-half the distance between adjacent anode segments of the same electrode system.

When two or more electrode systems are arranged with their anode segments distributed as shown in Fig. 1, it is possible to position such systems very close to each other without experiencing any undesirable cross coupling electric or magnetic alternating fields from one of the electrode systems to the adjoining ones. This is of significant advantage since in a magnetron tube structure where the electrode systems can be arranged close to one another, the air gap is shortened so that the magi: ic field shown by the arrow 3, and produced by means of a permanent magnet or electromagnet, not shown, may easily permeate the air gap. The direction of magnetic field, shown by the arrow 3, is seen to extend parallel to the axis of the tube and perpendicular to the direction of electron emission from the cathode 6, see Fig. 2. Hence, the electrons which move in a plane at right angles to the uniform magnetic field 3 execute circular paths when moving toward the anode segments in well known manner.

The instantaneous pattern of the alternating magnetic field lines, shown in Fig. 1, clearly indicates that disturbing magnetic cross coupling between the anode segments 1 and 2 of the respective electrode systems does not take place and as a result there will be no disturbing influence on the oscillations produced by the magnetron tube. The pattern of the magnetic alternating field lines for anode segments 1 is designated by reference numeral 4 and the pattern of the alternating magnetic field lines for anode segments 2 is designated by reference numeral 5.

Electric coupling between the segments of the respective electrode systems is avoided by arranging each anode seg ment of one of the electrode systems symmetrically with respect to two oppositely phased oscillating anode segments of the other electrode system.

Referring to Figs. 2a and 212, only two electrode systerns are shown to enable a better representation of the magnetron tube structure in accordance with the inven tion. The anode segments of the respective electrode systems are arranged in the manner disclosed with reference to the description of structure shown in Fig. 1.

One of the electrode systems includes the cathode portion 6' and the anode block 7 which is divided into a plurality of segments 1 which in turn define resonant cavities 8 surrounding the cathode portion 6'. The segments 1 are uniformly spaced from each other angularly about the cathode portion 6'. The other electrode system comprises a cathode portion 6 and an anode block 16 which in turn is divided into a plurality of segments 2 which define resonant cavities 8' surrounding the cathode portion 6. The segments 2 are also uniformly spaced from each other angularly about the cathode portion 6.

The surface of the cathode portions 6 and 6, arranged within the confines of the anode block lit) and '7 respectively, are activated, that is, these cathode portions have an electron emissive coating, for example an oxide coating, which is shown in the drawing by dots covering the portions of the cathode which are activated. The cathode portions 6" not surrounded by the anode blocks '7 and are not provided with an electron emissive coating. All of the cathode portions, 6, 6, and 6" are arranged along a common axis.

As is apparent from the drawing the anode block lid is spaced from the anode block 7 by a small distance along the common axis of the cathode. In addition the anode block 10' is angularly displaced with respect to anode block 7 by an angle being equal to one half the angular distance between adjoining segments of any one block.

If instead of arranging the anode block it) spaced from I the anode block 7, the former were to be in contact with the latter, but angularly displaced in accordance with the invention, then the separating gap at will be zero, in which case, the cathode will be covered with an emissive coating along its entire surface extending between the respective anode blocks, so as to provide a number of successive contiguous emissive areas equal to the number of anode blocks and respectively surrounded thereby.

The anode blocks, which may or may not form part of the tube envelope, may be formed of metal sheets which are stacked to form the blocks, such as 7 and M. These anode blocks are in turn formed with cylindrical holes 8 which communicate with the discharge space, or interaction space, by means of gap 9. The cylindrical holes 8 are dimensioned so that together with the gap 9, LC constants will be obtained which will produce oscillations at a frequency which coincides with the desired operating frequency. As will be appreciated from the drawing, the gaps 9 divide the inner surfaces of the respective anode blocks into individual anode segments, the adjacent segments of which produce oppositely phased oscillations.

In order to assure the generation of oscillations in the desired mode it is possible to connect similarly phased anode segments, by strapping the same, in a manner well known in the art.

In order to abstract the output power of the magnetron for connection to a suitable load, it is possible, for instance, to arrange in one of the resonant cavities 8 and 8' of each of the electrode systems a coupling device in the form of a coupling loop one end of which is connected to the wall of the anode block inside the vacuum portion of the tube structure while the other end may be brought external of the anode block or if the anode block does not form part of the vacuum envelope then also external of the vacuum envelope in vacuum tight manner. The coupling loop for the electrode system including the anode segments 1 is designated by reference numeral 10 Whereas the coupling loop for the other electrode system including the anode segments 2 is designated by reference numeral 11.

The conductors 12, 13 of the coupling loops 10, 11 respectively may be connected as noted either externally of the anode block or externally of the vacuum envelope to a. single output conductor, not shown. It the respective distances from the coupling loops 10 and 11 to the junction of conductors 12, 13 with the single output conductor are equal in length, or if the difference in length is equal to multiples of a wave length at the operating frequency of the magnetron tube, then the oscillations produced by the respective electrode systems will be of the same phase, that is, the magnitude of the oscillations generated by the respective electrode systems will be a maximum at the same instant of time.

In accordance with a further feature of the invention the respective distances from the coupling loops 10 and 11 to the junction of conductors 12, 13 with a single output conductor may be so dimensioned that the adjacent electrode systems produce oscillations which are displaced in phase by or 270 electrical degrees respectively. In other words the respective distances will vary by A of a wavelength at the operating frequency. In this case the fields of the adjacent electrode systems supplement one another in relation to the movements of the electrons. As a result the fringe disturbances at the borders of each electrode system are entirely eliminated.

In order to simplify the drawing only one-half of two anode systems has been illustrated and described. It is apparent from the description of the invention as set forth above that three or more electrode systems may be used which are arranged adjacent one another in the manner described hereinabove.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of high frequency signal generators differing from the types described above.

While the invention has been illustrated and described as embodied in high frequency satires tural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore,suchadaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. In a magnetron vacuum tube, in combination, a plurality of electrode systems each comprising an emissive cathode area and an anode block divided into segments surrounding said emissive cathode area, said segments of each anode block being uniformly spaced from each other angularly about said emissive cathode area, all of said emissive cathode areas being arranged along a common axis, and adjacent electrode systems being located along said common axis and angularly displaced with respect to each other by an angle equal to one-half the angular distance between adjoining segments of any one anode block, the number of said emissive cathode areas being equal to the number of anode blocks.

2. In a magnetron vacuum tube, in combination, a plurality of electrode systems each comprising an emissive cathode area in the form of an electron emissive coating and an anode block divided into segments surrounding said emissive cathode area, said segments of each anode block being uniformly spaced from each other angularly about said emissive cathode area, all of said emissive cathode areas being arranged along a common axis, and adjacent electrode systems being located along said cornmon axis and angularly displaced with respect to each other by an angle equal to one-half the angular distance between adjoining segments of any one anode block, the number of said emissive cathode areas being equal to the number of anode blocks.

3. In a magnetron vacuum tube, in combination, a plurality of electrode systems each comprising an emissive cathode area and an anode block divided into segments defining resonant cavities surrounding said emissive cathode area, said segments of each anode block being uniformly spaced from each other angularly about said emissive cathode area, all of said emissive cathode areas being arranged along a common axis, and adjacent electrode systems being located along said common axis and angularly displaced with respect to each other by an angle equal to one-half the angular distance between adjoining segments of any one anode block; and means provided in said anode blocks of said electrode systems for coupling the oscillations generated by said electrode systems to a suitable load, the number of emissive cathode areas being equal to the number of anode blocks.

4. In a magnetron vacuum tube, in combination, a plurality of electrode systems each comprising a cathode portion having an electron emissive coating and an anode block divided into segments defining resonant cavities surrounding said electron emissive cathode portion, said segments of each block being uniformly spaced from each other angularly about said electron emissive cathode portion, all of said electron emissive cathode portions being arranged along a common axis, and adjacent electrode systems being located along said common axis and angularly displaced with respect to each other by an angle equal to one-half the angular distance between adjoining segments of any one block; and coupling means portions of which are respectively arranged in one of the cavities defined by said segments of said anode blocks and adapted to interconnect said cavities with an output conductor so as to couple the oscillations of ,the respective electrode systems to said output conductor, the lengths of the respective coupling means to their respective junction points with said output conductor differing by where x is the operating wavelength of the magnetron tube so that the adjacent electrode systems produce oscillations displaced in phase or 270 respectively.

5. In a magnetron vacuum tube, in combination, a plurality of electrode systems each comprising an emissive cathode area and an anode block divided into, segments defining resonant cavities surrounding said: emissive cathode area, said segments of each block being uniformly spaced from each other angularly about said emissive cathode area, all of said emissive cathode areas being arranged along a common axis, and adjacent electrode systems being located along said common axis and angularly displaced with respect to each other by an angle equal to one-half the angular distance between adjoining segments of any one anode block, the number of emissive cathode areas being equal to the number of anode blocks; and coupling means arranged in said anode blocks of said electrode systems, said coupling means communicating with one of the cavities formed in said anode block and coupling the oscillations generated therein to a suitable load.

6. In a magnetron vacuum tube, in combination, a plurality of electrode systems each comprising a cathode portion and an anode block divided into segments defining resonant cavities surrounding said cathode portion, said segments of each block being uniformly spaced from each other angularly about said cathode portion, all of said cathode portions being arranged along a common axis, and adjacent electrode systems being located along said common axis and angularly displaced with respect to each other by an angle equal to one-half the angular distance between adjoining segments of any one anode block; and a coupling loop arranged in each of said anode blocks of said electrode systems, said coupling loop communicating with one of the cavities formed in each of said anode blocks and coupling therefrom the oscillations produced therein to a suitable load.

7. In a magnetron vacuum tube, in combination, at least two electrode systems each comprising a cathode portion having an electron emissive coating and an anode block divided into segments defining resonant cavities surrounding said electron emissive cathode. portion, said segments of each block being uniformly spaced from each other angularly about said electron emissive cathode portion, all of said electron emissive cathode portions being arranged along a common axis, and said blocks of said two electrode systems being located along said common axis spaced from and angularly displaced with respect to each other by an angle being equal to one-half the angular distance between adjoining segments of one block, the cathode portion between said two blocks being-nonemissive; and a coupling loop arranged in each of said anode blocks of said electrode systems, said coupling loop communicating with one of the cavities formed in each of said anode blocks and coupling therefrom the oscillations produced therein to a suitable load.

8. In a magnetron vacuum tube, in combination, a plurality of electrode systems each comprising a cathode portion having an electron emissive coating and an anode block divided into segments defining resonant cavities surrounding said electron emissive cathode portion, said segments of each block being uniformly spaced from each other angularly about said electron emissive cathode portion, all of said electron emissive cathode portions being arranged along a common axis, and adjacent electrode systems being located along said common axis and angularly displaced with respect to each other by an angle equal to one-half the angular distance between adjoining segments of any one block; and a coupling loop arranged in each of said anode blocks of said electrode systems, said coupling loop communicating with one of the cavities formed in each of said anode blocks and coupling therefrom the oscillations produced therein to a suitable load.

9. In a magnetron vacuum tube, in combination, at least two electrode systems each comprising a cathode portion and an anode block divided into segments defining resonant cavities surrounding said cathode portion, said segments of each block being uniformly spaced from each other angularly about said cathode portion, all of said cathode portions being arranged along a common y axis, and said blocks of said two electrode systems being located along said common axis adjacent to and angularly 15 displaced with respect to each other by an angle equal to one-half the angular distance between adjoining segments of any one block; and a coupling loop arranged in each of said anode blocks of said electrode systems, said coupling loop communicating with one of the cavities formed in each of said anode blocks and coupling therefrom the oscillations produced therein to a suitable load.

References Cited in the file of this patent UNITED STATES PATENTS 2,463,416 Nordsieck Mar. 1, 1949 2,485,401 McArthur Oct. 18, 1949 2,496,500 Spencer Feb. 7, 1950 2,606,307 Pease et al. Aug. 5, 1952 

